Ligno cellulosic materials and the products made therefrom

ABSTRACT

A process comprising treating a lignocellulosic material preferably pulp in the presence of a transition metal catalyst with a oxidizing agent selected from a group consisting of hydrogen peroxide, hypochlorite, hypochlorous acid and any combination thereof to form a treated lignocellulosic material having a viscosity equal to or less than about 17 cp and having reducing functional groups selected from the group consisting of aldehyde and aldehyde type functional groups at the C6 and C1 positions but predominating at the C1 position.

RELATED APPLICATION(S)

This application claims priority from U.S. Patent Application Ser. No.60/676,828, filed May 2, 2005; and U.S. Patent Application Ser. No.60/760,073, filed Jan. 19, 2006.

BACKGROUND OF THE INVENTION

Cellulose pulps have been used in a variety of personal care or medicalcare absorbent products, for instance, diaper fluff or incontinencearticles. One important issue of these applications is the odor causedby the body fluids. In the case of diaper fluff, ammonia odor from theurine is the major concern. For other applications, malodorous issue maybe caused by other nitrogen-containing or sulfur-containing substances.

From literature, it is found that a variety of additives have been usedto absorb the odors. See for example, U.S. Pat. Nos. 6,765,042 and6,852,904, and US Patent Application No. 00268281 A 1.

SUMMARY OF THE INVENTION

One aspect of this invention relates to a process comprising treating alignocellulosic material, preferably in fibrous or particulate form andmore preferably a hardwood, a softwood pulp or a combination thereof, inthe presence of a transition metal catalyst with an oxidizing agentselected from a group consisting of hydrogen peroxide, hypochlorite,chlorine dioxide, hypochlorous acid and any combination thereof to forma treated lignocellulosic material having a viscosity equal to or lessthan about 17 cps and preferably having reducing functional groupsselected from the group consisting of aldehyde and aldehyde typefunctional groups such as hemiacetals that predominate at the C1position. As used herein the term “lignocellulosic material” means anorganic polymeric or oligomeric material having substituted orunsubstituted carbohydrate (such as glucose, mannose, xylose, arabinose,galactose and the like) units as for example cellulose, hemicelluloseand polysaccharides. As used herein, the term “predominate” means morethan 50% based on the total weight of reducing functional groups. In thepreferred embodiments of the invention, the treated lignocellulosicmaterial preferably has a copper number of more than about 0.5 and/or acarboxyl content of more than about 3.5 meq/100 gram.

Another aspect of the invention relates to a treated lignocellulosicmaterial having a viscosity equal to or less than about 17 cps. Thematerial preferably has reducing end groups selected from the groupconsisting of aldehyde and aldehyde type functional groups such ashemiacetals that predominate at the C1 position i.e., at least about 50%based on the total number of aldehyde and aldehyde type functionalgroups contained in the treated lignocellulosic material. The amount ofaldehyde and aldehyde type functional groups at the C1 position ispreferably greater than about 75%, more preferably equal to or greaterthan about 80% and most preferably equal to or greater than about 90%based on the total amount of aldehyde and aldehyde type functionalgroups contained in the treated lignocellulosic material. In theembodiment of choice, the amount of aldehyde and aldehyde typefunctional groups are at the C1 position equal to about 95%. In thepreferred embodiments of the invention, the treated lignocellulosicmaterial preferably has a copper number of more than about 4 and/or acarboxyl content of more than about 4.5 meq/100 grams.

The treated lignocellulosic materials of this invention exhibit one ormore beneficial properties. For example, the materials may exhibit odorcontrol properties. While we do not wish to be bound by any theory it isbelieved that some materials control odor by complexing with odoriferousmaterials as for example ammonia from urine and/or by inhibiting thegrowth of bacteria that convert urea into ammonia. The odor controlcharacteristics of these lignocellulosic materials especially pulp makesthem especially useful in the construction of absorbent personal hygienearticles such as diapers, feminine hygiene articles, adult incontinencyproducts and the like, with or without SAP. Certain embodiments of thetreated lignocellulosic material of this invention exhibit good wetstrength and/or drainage properties. Certain other embodiments of theinvention where the ligno cellulosic material is pulp surprisingly stillmaintain most of the paper mechanical properties unchanged compared withthe untreated pulp, except with the possible exception of tear strength.

Yet another aspect of this invention relates to a personal hygienearticle for absorbing fluids, the article comprising:

at least one fluid permeable top sheet layer and at least onesubstantially fluid impermeable back sheet layer; and

an absorbent sub layer material interposed between the top sheet layerand the back sheet layer, the sub layer material comprising the treatedlignocellulosic material of this invention.

Still another aspect of this invention relates to a method for making anabsorbent composite useful for personal hygiene articles whichcomprises:

dry shredding the treated lignocellulosic material of this invention toform an absorbent sub layer material comprised of fluffed base-treatedwood pulp;

providing at least one fluid permeable top sheet layer and at least onesubstantially fluid impermeable back sheet layer; and

interposing the sub layer material between the top sheet layer and backsheet layer.

Still another aspect of this invention relates to a paper or paperboardmaking process which comprises the steps of:

(a) forming an aqueous paper making stock furnish comprising pulp havinga viscosity equal to or less than about 17 cp and having reducing endgroups selected from the group consisting of aldehyde and aldehyde typefunctional groups at the C6 and C1 positions but predominating at the C1position;

(b) depositing said furnish on a forming wire of a paper making machineto form a wet paper web; and

(c) drying said wet paper or paperboard web to form a dried paper orpaperboard.

Yet another aspect of this invention relates to a paper or paperboardcomprising pulp having a viscosity equal to or less than about 17 cp andhaving reducing end groups selected from the group consisting ofaldehyde and aldehyde type functional groups at the C6 and C1 positionsbut predominating at the C1 position.

DETAIL DESCRIPTION OF THE INVENTION

One aspect of this invention relates to a process comprising treating alignocellulosic material, preferably wood pulp, in the presence of atransition metal catalyst with an oxidizing agent selected from a groupconsisting of hydrogen peroxide, chlorine dioxide, hypochlorite,hypochlorous acid and any combination thereof.

The lignocellulosic material can be in fibrous or particulate form asfor example pulp fibers, fines and other pulp fragments; hemicellulose,starch and polysaccharide particles and powders. The lignocellulosicmaterial can also be in solution as for examples solutions of cellulosederivatives such as carboxymethyl cellulose, hydroxypropyl cellulose andthe like.

The type of lignocellulosic material used in the process of thisinvention is not critical and any such material can be used. Forexample, useful lignocellulosic materials include those derived fromknown sources of such materials as for example plants. Illustrative ofuseful lignocellulosic materials are polysaccharides such as starches.Useful starches for the practice of this invention are naturallyoccurring carbohydrates synthesized in corn, tapioca, potato and otherplants by polymerization of dextrose units. All such starches andmodified forms thereof such as starch acetates, starch esters, starchethers, starch phosphates, starch xanthates, anionic starches, cationicstarches and the like which can be derived by reacting the starch with asuitable chemical or enzymatic reagent can be used in the practice ofthis invention. Useful polysaccharides can be hemicellose extracted fromwood porior to pulping or extracted from the pulp fibers after pulpingand can be corn fiber kernels which can be enriched with xylanes,celluloses, starches or a combination of any two or more thereof. AlsoIllustrative of lignocellulosic materials for use in the practice of theprocess of this invention are pulp fibers used in the formation oftissues, towels, diapers, feminine hygiene and adult incontinenceproducts and used to make other types of pulp products, paper andpaperboard. Such pulp fibers include those derived from hardwood trees,softwood trees, or a combination of hardwood and softwood trees preparedfor use in a papermaking furnish by any known suitable digestion,refining, and bleaching operations as for example known mechanical,thermo mechanical, chemical and semi chemical, etc., pulping and otherwell known pulping processes. The term “hardwood pulps” as used hereinrefers to fibrous pulp derived from the woody substance of deciduoustrees (angiosperms), whereas “softwood pulps” are fibrous pulps derivedfrom the woody substance of coniferous trees (gymnosperms). Useful pulpfibers may be provided from non-woody herbaceous plants including, butnot limited to, kenaf, hemp, jute, flax, sisal, or abaca although legalrestrictions and other considerations may make the utilization of hempand other fiber sources impractical or impossible. Either bleached orunbleached pulp fiber as for example unbleached kraft and bleached kraftpulp, or recycled pulp may be utilized in the process of this invention.The pulp may have been subjected to any treatment history that is normalin pulping and bleaching or may be intentionally modified as for exampleby controlled prehydrolysis or caustic extraction of chips before kraftpulping, acid or enzyme (cellulases or hemicellulases) hydrolysis ofkraft pulps, “cold-soda” treatment of pulp (up to mercerizing strength).

Preferred lignocellulosic materials are hardwood pulp, softwood pulp ora combination thereof. More preferred lignocellulosic materials arekraft hardwood pulps, softwood pulp or a combination thereof. Mostpreferred lignocellulosic materials are bleached kraft hardwood pulps,softwood pulps or a combination thereof, especially bleached kraftsoftwood pulps.

Transition metal catalyst used in the practice of this invention mayvary widely and any transition metal can be used. Illustrative of suchmetals are Cu, Fe, Zn, Co, Ni, Mn, V, Mo, W, Zr, Ce, Cr and anycombination thereof. The metals are preferably used in the form ofsalts, preferably water soluble metal salts. Preferred metal saltsinclude halide, sulfate, nitrate and phosphate and carbonate metal saltsand combinations thereof. Most preferred metal salts are Cu (Cu+ and Cu2+, Fe (Fe 3+, Fe 2+) and Zn (Zn2+) metal salts with Cu and Fe metalsalts being those of choice.

The amount of metal catalyst used in the process of this invention mayvary widely and any amount sufficient to form the desired treatedlignocellulosic product can be used. The amount of metal catalyst isusually at least about 0.005% by wgt of the dried lignocellulosicmaterial even though higher or lower amounts may be used. The amount ofmetal catalyst is preferably from about 0.005 to about 1% by wgt of thedried lignocellulosic material, more preferably about 0.01 to about 0.5%by wgt of the dried lignocellulosic material and most preferably about0.01 to about 0.1% by wgt of the dried lignocellulosic material.

Oxidizing agent for use in the process are selected from a groupconsisting of hydrogen peroxide, chlorine dioxide, hypochlorite,hypochlorous acid and any combination thereof. The preferred oxidizingagents are hydrogen peroxide and hypochlorite and the most preferredoxidizing agent is hydrogen peroxide.

The amount of the oxidizing agent may vary widely and any amountsufficient to form the desired treated lignocellulosic product can beused. The amount of the oxidizing agent is usually at least about 0.1%by wgt of the dried lignocellulosic material although lower amounts mayused if effective to provide the desired ligno cellulosic material. Theamount of the oxidizing agent is preferably from about 0.1 to about 10%by wgt of the dried lignocellulosic material, more preferably about 0.1to about 5% by wgt of the dried lignocellulosic material and mostpreferably about 0.5 to about 5% by wgt of the dried lignocellulosicmaterial.

Treatment temperatures may vary widely and any temperature sufficient toform the desired treated lignocellulosic product can be used. Thetreatment temperature is usually at least about 20° C. although lowertemperatures may be used if effective to provide the desired lignocellulosic material. The treatment temperature is preferably from about20° C. to about 120° C., more preferably from about 40° C. to about 120°C. and most preferably from about 40° C. to about 90° C., with atreatment temperature of from about 60° C. to about 90° C. being thetreatment temperature in the embodiments of choice.

Treatment pH may vary widely and any temperature sufficient to form thedesired treated lignocellulosic product can be used. The treatment pH isusually between about 1 and about 9 although lower or higher pHs may beused if effective to provide the desired ligno cellulosic material. Thetreatment pH is preferably from about 2 to about 8, more preferably fromabout 2 to about 7 and most preferably from about 2 to about 6.

Treatment times may vary widely and any time sufficient to form thedesired treated lignocellulosic product can be used. The treatment timeis usually at least about 5 minutes although longer treatment times maybe used if effective to provide the desired ligno cellulosic material.The treatment time is preferably from about 5 minutes to about 20 hours,more preferably 15 minutes to about 10 hours and most preferably fromabout 30 minutes to about 4 hours.

Optionally the process of this invention can be carried out in thepresence of UV radiation preferably when peroxide is used as theoxidizing agent. The UV treatment has the advantage of being moreeffective at lower temperatures such as room temperature (or ambienttemperature) without need for heating equipment and can be used towidening the pH effective range. For example, the process can beeffectively carried in the presence of UV radiation at ambienttemperature (or without heating), at neutral pH in a very short time offrom a few seconds to 1 hour, depending on UV lamp power and fibermixing conditions. The UV lamp used in the process, preferably is a highintensity lamp, such as medium pressure mercury arc lamp or itsvariants, pulsed Xenon flash lamps, or excimer lamps. It is mostpreferable to use the medium pressure mercury arc lamp which is low costand readily available from commercial sources. The UV lamps, which areinserted in quartz sleeves, can be inserted (submerged) into the pulpsuspension for irradiation. Sometimes, it may be more advantageous toput UV lamps above the mixing suspension of the lignocellulosicmaterial. For this type of UV irradiation, both mercury arc lamps andelectrode-less powered lamps (such as from Fusion UV company) can beused. It is preferred that the pulp fibers are fully mixed and wellstirred during reaction since UV penetration in water is very low andmost chemical action has to come from UV decomposing the peroxide inwater solutions. The UV treatment can be done with addition of catalystto the UV-peroxide system as well. Useful catalysts may vary widely andany conventional UV catalyst can be used as for example water-solublemetal salts such as iron salts or copper salts used in the process;micro- or nano-particulate titanium dioxide or zinc oxidephoto-catalysts; azo based organic catalyst, such as water-soluble4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-methylpropionamidinedihydrochloride, AIBN or Dupont Vazo catalyst 88; and2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO).

The process can be conducted batch wise, continuously or semicontinuously. The process of this invention can also be practiced aspart of a pulping process as a process step at the end of a mechanical,semi-chemical or chemical pulping process or as a part of a bleachingprocess as a process step at the end of the bleaching process. Theprocess can also be used to treat market paper making pulp or fluff pulpas for example by re-slushing market paper making pulp or fluff pulp ina hydro-pulper or like-device. The treatment in the hydro-pulper orlike-device has the flexibility of adjusting conditions. For instance,the treatment started at acidic pH and after some appropriate period oftime adjusting to alkaline pH by the addition of caustic and continuingthe reaction at higher pH. This combined acidic-alkaline treatment canbe used to change the ratio of carboxyl vs. carbonyl groups in thetreated lignocellulosic material.

The treated lignocellulosic material formed by the process of thisinvention has a viscosity less than 17 cps as measured by the procedureof TAPPI T-230. This is in contrast to the viscosity of untreated pulpwhich is usually greater than about 17 cps. The treated lignocellulosicmaterial preferably has a viscosity of equal to or less than about 15cps, more preferably equal to or less than about 12 or equal to or lessthan about 10 cps and most preferably from about 1 to about 10 cps. Inthe embodiments of choice, the treated lignocellulosic material formedby the process of this invention has a viscosity of from about 2 toabout 7 cps. It is believed that the lowered pulp viscosity indicates agreater amount of reducing functional groups at the C1 position at theend of the molecular or oligomeric chains forming the treatedlignocellulosic material. While we do not wish to be bound by any theoryit is believed that this would provide more binding sites for sometransitional metals, for instance copper and some others and that theend reducing functional groups act as the other functional sites, inaddition to other oxidized groups on the polysaccharide units. It maysometimes be advantageous to increase the amount of end reducingfunctional groups ends provided by this invention be further treatingthe treated lignocellulosic material in an acid hydrolysis or enzymatichydrolysis step which is believed will further increase the odor controlproperties of the treated lignocellulosic material.

The treated lignocellulosic material formed by the process of thisinvention preferably has a degree of polymerization of less than about1200. In these preferred embodiments of the invention the treatedlignocellulosic material more preferably has a degree of polymerizationequal to or less than about 1000 and most preferably equal to or lessthan about 900. In the embodiments of choice of these preferredembodiments of the invention, the treated lignocellulosic materialformed by the process of this invention has degree of polymerization offrom about 100 to about 800 or from about 200 to about 600. In apreferred embodiment of the invention, the treated lignocellulosicmaterial formed by the process of this invention has reducing groupsselected from the group consisting of aldehyde and aldehyde typefunctional groups such as hemiacetals that predominate at the C1position which results when the lignocellulosic chain is oxidatively cutduring the process to reduce the degree of polymerization and theviscosity of the treated pulp. The amount of such end groups can bedetermined by the procedures set forth in U.S. Pat. No. 6,635,755 andreferences cited therein and other methods known to those of ordinaryskill in the art. According to the invention it is possible that thereducing functional groups can isomerize into groups other than ofaldehyde and aldehyde type functional groups. Because of the randomnessof the oxidation process, it is also possible that aldehyde or aldehydetype function groups may be present at the C6 position and/or ketonefunctions may be present at the C3 and/or C4 positions all though at alesser extent. Preferably the amount of aldehyde and aldehyde typefunctional groups reducing groups present at the C1 position is greaterthan about 75% based on the total amount of aldehyde and aldehyde typefunctional groups. The amount of aldehyde and aldehyde type reducingfunctional groups present at the C1 position is more preferably equal toor greater than about 80% and most preferably equal to or greater thanabout 90% on the aforementioned basis. In the embodiment of choice, theamount of aldehyde and aldehyde type reducing functional groups at theC1 position equal to about 95% based on the total amount of aldehyde andaldehyde type reducing functional groups.

In the preferred embodiments of the invention, the treatedlignocellulosic material formed by the process of this invention has acopper number equal to or greater than about 3. The copper number ismeasured by the following procedure of Tappi T-430 cm-99. The treatedlignocellulosic material preferably has a copper number equal to orgreater than about 4.4, more preferably equal to or greater than about 5and most preferably equal to or greater than about 5.5.

In the preferred embodiments of the invention, the treatedlignocellulosic material formed by the process of this invention hascarboxy number equal to or more than about 3.5 meq/100 grams of ovendried treated material. The carboxy number is measured by the followingprocedure Tappi T-237 cm-98. The treated lignocellulosic materialpreferably has a carboxyl number of above 4, more preferably above 5 andmost preferably above 5.5 meq/100 g.

In a preferred embodiment of this invention, the treated lignocellulosicmaterial formed by the process of this invention has odor controlproperties as measured by the ability to bind or complex with ammoniaand by its bacterial inhibition activity. The ability of the material tocomplex with ammonia is determined by the following test: A Kamas labhammermill equipped with a forming funnel was used to form the fiberizedpulp into 50 cm2, 3.00 gram pads formed from the lignocellulosicmaterial. The pads were placed inside a jar that is sealed with a lidcontaining a septum as a sampling port. The pads were dosed with 500micro-liter of a 0.6% ammonia solution through a gas tight syringehaving a needle of sufficient length to touch the pad surface. After anequilibration period of 45 minutes, 1 qt headspace gas was sampledthrough the port using a calibrated hand pump and an ammonia indicatortube (i.e., Drager tube sampling system), withdrawing the sample througha needle adapter attached to the tube. In the preferred embodiments ofthe invention the amount of ammonia adsorbed by the treated thelignocellulosic material is 50% higher, preferably 60% higher and morepreferably 80% higher than the amount of ammonia adsorbed by same orsubstantially same lignocellulosic material prior to treatment in theprocess of this invention. In the embodiments of choice, the amount ofammonia absorbed is above 90% higher than the untreated pulp.

The bacterial inhibition property of the treated lignocellulosic isdetermined using the test organisms Corynebacterium ammoniagenes, ATCC6871 propagated in Urea Medium (I-144C) and grown at 37±2° C. for 2-3days in a shaker flask and Escherichia coli ATCC 11229 propagated inTryptic Soy Broth (I-053B) and grown at 37±2° C. for 18-24 hours in ashaker flask. The organisms were assigned unique codes to provide forcorrect generation of data. ASTM Method E 2180-01 was used to determinethe microbial load and percent reduction, Log₁₀ reduction or Log₁₀increase in numbers on the test substance against the test organism(s)modified as follows:

-   -   The 15×100 mm sterile Petri dish containing the sample ([50 mm]        2″ diameter) will be placed inside a larger Petri dish        containing 10 mL of water to increase the humidity and prevent        drying during the exposure period.    -   1) The samples will be hydrated, prior to inoculation with 0.5        mL of the test culture.    -   2) No “Agar Slurry” will be used.    -   3) The samples will be evaluated in duplicate.    -   4) The samples will be held at 35±2° C. in a humidified chamber        for 3 and 8 hour exposure periods (±10 minutes).    -   5) The neutralizer will be 50-mL volumes of Tryptic Soy Broth        with 10% Tween 80, 3% Lecithin, and 0.5% Sodium Thiosulfate, and        0.1% Histidine, pH 7.2±0.1 (I-148) in sterile 2 oz. jars.    -   6) Sonicate the sample in neutralizer for 1 minute followed by        vortexing for 1 minute prior to diluting.    -   7) Serial dilutions will be prepared to 10⁻⁵ through 9-mL        volumes of 2× Difco Neutralizing Buffer. Dilutions will be        prepared to 10⁻⁶ for the Control with plating in duplicate by        the Spread Plate Method using Urea Agar (I-145C) and Mac Conkey        Agar (I-090B). The undiluted sample in neutralizer (10⁰ dilution        [50 mL]) will be plated by spreading 1 mL across 3 plates.    -   8) Incubation will be at 35±2° C. for 3 days for Urea Agar and        at 35±2° C. for 18-24 hours for Mac Conkey Agar.    -   9) Neutralizer effectiveness will be conducted concurrently with        testing using E. coli as the test organism.

The validity of the results obtained by the above procedure relies on ademonstration that the test substance(s) does not, under the conditionsof the test, inhibit the multiplication of viable organisms that may bepresent; and, that the media used to conduct the study demonstrateappropriate neutralizing and growth promoting characteristics. Toconduct neutralizer effectiveness testing for bacterial recovery, a 2″diameter sample of test substance will be placed in 50 ml of neutralizer(#6) above) and sonicated followed by vortexing. A dilution of the testorganism, to deliver ˜10-100 Colony Forming Units (CFU)/mL in the finalconcentration of neutralizer will be added to the jar and mixedthoroughly. A jar of neutralizer without test substance, similarlyinoculated, will serve as the positive control. Duplicate 0.5 mLaliquots from the jar will be spread plated on Mac Conkey Agar for thetest substances and the positive control. If growth of the test organismon the plates containing test substance, and growth from the positivecontrol are comparable in both number and colonial development, then theneutralizer system is considered adequate. Following incubation, plateswill be counted and recorded as CFU/mL. The CFU/sample will then becalculated from this figure. Percent reductions and Log₁₀ reductions orincreases in the numbers of microorganisms (both types) per sample, ascompared to the “Control,” will be calculated for each exposure period.The bacterial inhibition property is preferably 40% higher than theuntreated pulp, more preferably 50% higher and most preferably 60%higher.

In certain preferred embodiments where the lignocellulosic material ispulp preferably wood pulp, the treated lignocellulosic material of thisinvention exhibits good wet tensile strength improvement. The exactlevel of improvement may vary widely, and, in addition to being affectedby the level of treatment, is also dependent on the type of fiberfurnishes used and the type of sheets made for evaluation. For theunrefined pulp furnishes, while the wet tensile of the control isextremely low, the improvement can be at least about 1.5 or 2 timeshigher, and preferably can be at least 3-5 times higher than the controlas measured by the procedure of Tappi T-456 om-03. For non-Tappihandsheets, such as for tissue and other applications, the level ofimprovement can vary, depending on refining and wet pressing levels.

In certain preferred embodiments, the treated lignocellulosic materialof this invention exhibits good drainage as measured by the procedure ofT 221 cm-99.

In certain preferred embodiments, the treated lignocellulosic materialof this invention contains bound metal derived from the catalyst. Thebound metal is believed to have a beneficial impact on the bactericidalactivity of the treated lignocellulosic material. As used herein,“bound” means the metal element that stays with the pulp and is notwashed out by pulp washing operations. The nature of the metal bindingto the pulp is known to be related to ionic interactions andcomplex-forming with pulp functional groups such as carbonyl or carboxylgroups as is enhanced by the present invention. The amount of boundmetal is determined by the general analytical methods, such as theICP-Atomic Absorption method and is preferably at least 10 ppm,preferably from about 20 ppm to about 700 ppm, more preferably fromabout 20 ppm to about 150 ppm and most preferably from about 20 ppm toabout 100 ppm.

The treated lignocellulosic material of this invention can be subjectedto a number of subsequent processes to further modify the properties ofthe material. For example, the treated lignocellulosic material can besubsequently treated with a cationic agent which is believed to bind thereducing functional groups of the treated materials. Useful cationicmaterial can vary widely and include cationic nitrogen containingpolymers such polyamines, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimidehydrochloride (EDC), hexadimethrine bromide, polyethyleneimines (bothelinear and branched), copolymers of diallyldimethyl ammonium chloride(DADMAC), copolymers of vinyl pyrrolidone (VP) with quaternizeddiethylaminoethylmethacrylate (DEAMEMA), polyamides, cationicpolyurethane latex, cationic polyvinyl alcohol, polyalkylamines,dicyandiamid copolymers, amine glycigyl addition polymers,poly[oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylene]dichlorides, high charge-density polyvinylamine, polyallylamine (PAH),poly (hexamethylene biguanide hydrochloride) (i.e. PHMB), polyamidoamine(or polyethylenimine); cationic metal ions, such as water-solublealuminum salts, calcium salts, and zirconium salts; and these bound ionscan act as active complexing sites for sizing and other papermakingchemicals; and cationic dendrimers, such as PAMAM (polyamidoamine)dendrimers with amino surface groups, and polypropylenimine dendrimerswith amino surface groups. It is believed that treatment with suchcationic materials may modify properties such as increase of paper bulkwhich is desirable for fine paper, paperboard, tissue, towel, andabsorbent products, while maintaining good strength and having decreasedwater-retention value (WRV) and increased freeness.

Also, the treated lignocellulosic material can be subsequently treatedwith micro- or nano-particulate metal oxides such as aluminum oxide,titanium oxide, zinc oxide, or silica and are retained by the treatedlignocellulosic material to modify properties such as colorant, dye oroptical brightener fixation, printability and/or odor controlcharacteristics of the treated lignocellulosic material. The treatedlignocellulosic material can be subsequently treated with a crosslinking material as for example a water-dispersible or water-solublebi-, multifunctional carbodiimide and/or polycarbodiimide such as1,6-hexamethylene bis(ethylcarbodiimide); 1,8-octamethylenebis(ethylcarbodiimide); 1,10 decamethylene bis(ethylcarbodiimide); 1,12dodecamethylene bis(ethylcarbodiimide);PEG-bis(propyl(ethylcarbodiimide)); 2,2′-dithioethylbis(ethylcarbodiimde); 1,1′-dithio-p-phenylene bis(ethylcarbodiimide);and 1,1′-dithio-m-phenylene bis(ethylcarbodiimide). during papermakingor fibrous network forming. The bi- or multi-functional carbodiimidegroups react with the reducing functional gropes of the material, andcross-linking and locking the fibers of the material inside the paper orfiber network structure.

The treated lignocellulosic material of this invention can be used forconventional purposes in situ or after isolation using conventionalproduct isolation techniques. For example, treated lignocellulosicmaterial of this invention can be used to make paper or paperboardsubstrates or webs. Methods and apparatuses for preparing a substrateformed of ligno cellulosic fibers are well known in the paper andpaperboard art. See for example “Handbook For Pulp & PaperTechnologies”, 2^(nd) Edition, G. A. Smook, Angus Wilde Publications(1992) and references cited therein. Any conventional method andapparatus can be used. Preferably the process comprises: a) providing anaqueous suspension of ligno cellulosic fibers; b) depositing saidfurnish on a forming wire of a paper making machine to form a wet paperor paperboard web; c) drying the wet paper or paperboard web to obtaindried paper or paperboard web and d) calendering the dried paper orpaperboard web. In addition to these process steps, additional processsteps known to those of ordinary skill in the art may be employed as forexample a coating step to coat one or more surfaces of the dried paperor paperboard web with a coating comprising a binder containingdispersant pigment or treating the dried paper or paperboard at the sizepress with a sizing agent such as starch.

For example the materials can be used prepared absorbent articles as forexample diapers, tissues, towels, personal hygiene products usingconventional processes. Such products and their methods of manufactureare known to those of skill in the art and will not be described indetail. See for example, U.S. Pat. Nos. 6,063,982 and 5,766,159 andreferences described therein. The treated kraft pulp fibers of thisinvention can be used to make saturating kraft paper. Saturating kraftpaper is a paper sheet made from unbleached kraft pulp (mixture ofmostly hardwood and some softwood such as southern pine) that is used assubstrate for impregnation and curing with resin polymers. Saturatingkraft paper is used as home and office building materials, such askitchen counter tops. A useful property of saturating kraft paper iscontrol the liquid (a polymer resin solution) penetration rate into thesheet, while maintaining paper porosity and density. All of the hardwoodkraft fiber in the saturating sheet can be replaced by softwood as forexample southern pine kraft (linerboard grade pine kraft) treated by theprocess of this invention to provide saturating kraft paper having withgood liquid transport properties. While we do not wish to be bound byany theory, it is believed that the hemicelluloses carbohydrate layerstopochemically located on and inside the kraft fiber are oxidized in theprocess of this invention increasing the resin liquid absorption intothe sheet.

The present invention will be described with references to the followingexamples. The examples are intended to be illustrative and the inventionis not limited to the materials, conditions or process parameters setforth in the examples.

Example 1

Bleached Southern Pine Kraft pulp was treated with 1% hydrogen peroxideand 0.03% ferrous sulfate applied on pulp, at a pH 4 and a temperatureof 75° C. for 1 hour. The treated pulp was then washed with de-ionizedwater, and made into paper sheets and dried. The viscosity, coppernumber and carboxyl number of the treated pulp was determined using theaforementioned procedures. The viscosity of the pulp was 6.2 cp. Thecopper number of the pulp was 4.5. The carboxyl number of the pulp was5.5 meq/100 g. The pulp was also evaluated to determine the amount ofbound metal. The sample contains 43.4 ppm Fe as bound on the pulp, whichis not washed out by water. The bacterial inhibition properties of thepulps were evaluated using the procedure set forth herein above. Thebacterial inhibition test results were shown in the table 1 below.

TABLE 1 % (E-coli + % E-coli Ammoniagenes) Reduction, Reduction, 8 hours8 hours Vs. Untreated Vs. Untreated Control Control pulp Pulp TreatedPulp, 38% 23% 1% peroxide, 0.03% ferrous sulfate

Example 2

Bleached Southern Pine Kraft pulp was treated with 1% hydrogen peroxideand 0.03% copper sulfate applied on pulp, at pH 4 and temperature of 80°C. for 1 hour. The viscosity of the pulp was 5.7. The copper number ofthe pulp was 4.6. The carboxyl number of the pulp was 4.1 meq/100 g. Thetreated pulp was washed with de-ionized water, and made into paper sheetand dried. The sample contains 90.8 ppm Cu as bound on the pulp.

The pulp was tested for ammonia odor control and bacterial controlfunctions vs. the untreated pulp as control using the proceduredescribed above. The results are shown below in Table 2.

TABLE 2 % E-coli % (E-coli + Reduction, Ammoniagenes) 8 hours Reduction,Metal vs. 8 hours content in untreated vs. untreated pulp pulp pulpTreated Pulp, 1% 90.8 ppm 58% 68% peroxide, 0.03% Cu copper sulfateTreated with   93 ppm 44% 17% 0.03% copper Cu sulfate only

Example 3

Bleached Southern Pine pulp was treated with copper or iron catalyzedhydrogen peroxide oxidation, at pH 4 and 80° C. for 1 hour. The treatedpulp was then washed with de-ionized water and made into dry pulp sheetsfor fiberization by a lab-scale Kamas mill. In this example, 1% and 2%peroxide were used, and catalyst amount was also varied. The pulps weretested for ammonia odor control using the procedure described above. Theresults are shown below in Table 2.

The results of ammonia odor control were listed in the table 3 below.

TABLE 3 Ammonia gas Pulp- Ammonia gas % NH3 concentration % NH3 boundconcentration Reduction in Reduction Trace in headspace, vs. headspace,5 vs. Metal 2 strokes Untreated strokes Untreated ppm on sampling pulpsampling pulp pulp Untreated 35.3 ppm — 73.5 ppm —  3 ppm Pulp NH3 NH3Fe Control 11 ppm Cu Treated  2.5 ppm 93%  7.3 ppm 90% 43 ppm with 1%NH3 NH3 Cu peroxide, 0.02% copper sulfate Treated   2 ppm 94%  4.7 ppm94% 65 ppm with 1% NH3 NH3 Cu peroxide, 0.04% copper sulfate Treated   1ppm 97%  1.8 ppm 98% 48 ppm with 2% NH3 NH3 Cu peroxide, 0.02% coppersulfate Treated  0.7 ppm 98%  1.7 ppm 98% 55 ppm with 2% NH3 NH3 Cuperoxide, 0.04% copper sulfate Treated  7.1 ppm 80% 14.7 ppm 80% 43 ppmwith 1% NH3 NH3 Fe peroxide, 0.03% ferrous sulfate

Example 4

Experiments were conducted applying the metals at 80° C., pH 4 for 1hour, with both low doses (as in example 3) and very high doses of themetals applied in the absence of the oxidizing agent. The pulps weretested for ammonia odor control vs. the untreated pulp as control usingthe procedure described above. The results are shown below in Table 4.

TABLE 4 Ammonia gas Pulp-bound concentration in Metal the headspace ppmon pulp Untreated Pulp   35 ppm  3 ppm Control NH3 Fe Treated only with  16 ppm  93 ppm 0.03% copper NH3 Cu sulfate by our process - washed (Nooxidants) Treated only with 14.5 ppm 109 ppm 0.03% ferrous NH3 Fesulfate by our process - washed (No oxidants) Treated only with   5 ppm283 ppm 0.3% copper NH3 Cu sulfate by our process - washed (No oxidants)Treated only with   4 ppm 635 ppm 0.3% ferrous NH3 Fe sulfate by ourprocess - washed (No oxidants)

Example 5

Experiments were conducted applying the metals at 80° C., pH 4 for 1hour. The viscosities of the pulps were determined and the pulps weretested for ammonia odor control vs. the untreated pulp as control usingthe procedure described above. The results are shown below in Table 5.

TABLE 5 Ammonia gas pH of concentration in pulp after Pulp the headspacewashing viscosity Untreated pulp 43 ppm NH3 pH 6.4   18 cp controlTreated with 41 ppm NH3 pH 6.3 16.7 cp 0.02% zinc sulfate, with 2%peroxide Treated with 11 ppm NH3 pH 6.4  4.9 cp 0.02% zinc sulfate,0.01% ferrous sulfate, 2% peroxide

Example 6

This example is to demonstrate the wet strength benefit of ametal-catalyzed peroxide treatment, especially in the preferred pH rangeof the present invention. Bleached southern pine Kraft pulps weretreated with 2% and 3% hydrogen peroxide with 0.03% ferrous sulfate at80° C. for 1 hour. The pH range was varied from pH 4 to pH 10 at the endof the reaction. Standard 1.2 gram Tappi handsheets were made using theprocedure of Tappi T 205 sp-02 and the dry tensile strength, dry tearstrength and wet tensile strength were determined using the proceduresof Tappi T 494 om-01, Tappi T414 om-01 and Tappi T 456 om-03,respectively. The tensile wet/dry strength values were calculated frothe determined dry tensile strength, dry tear strength and wet tensilestrength values. The results were shown in the table 6 below.

TABLE 6 2% 2% 3% 3% peroxide, peroxide, peroxide, peroxide, 0.2% 0.6%0.2% 0.6% caustic caustic caustic caustic Untreated 2% applied, applied,3% applied, applied, Pulp, peroxide, end end pH peroxide, end end ph pH6 end pH 4 pH 4.8 10.3 end pH 4 pH 4.7 10 Dry 9.1 10.1 12.1 13.6 9 12.912.5 Tensile, lbs/inch Dry 125.5 89.7 154.3 155.1 95.3 156.3 152.8 Tear,gms Wet 0.1 0.4 0.3 0.3 0.5 0.4 0.3 Tensile, lbs/inch Tensile, 1.6 4.42.4 1.9 5.4 2.9 2.4 Wet/Dry Percent

Example 7

Drying of the treated pulp will decrease the carboxyl groups generatedon the fibers. This would not be relevant to the integrated paper/boardcases or to the dry fluff pulps and dry forming cases, where the treatedpulp would only be dried once. However, it would have an impact on thepaper or tissue/towel cases, where the dried treated pulp is purchased,and then re-slushed and made into paper products again by the wetprocesses and dried again. The results of drying on pulp carboxylcontents are shown in Table 7 below.

TABLE 7 Carboxyl, Carboxyl, meq/100 g, meq/100 g, Dried Wet Pulp andRewetted Pulp Untreated Bleached 3.3 3.7 Pulp Treated with 2% 5.5 3.7peroxide, 0.03% ferrous sulfate, at pH4, 80° C., for 1 hour.

Example 8

Unbleached kraft pulp was used to demonstrate the wet strengthimprovement on brown pulp as well. The brown high kappa pulp was treatedwith 2% peroxide, 0.04% ferrous sulfate at pH 4 and 80° C. for an hour.The treated pulp and the untreated pulp control were refined by a Valleybeater and made into 300 gsm square hand sheets, wet-pressed and driedon a flatbed dryer. The effect on sheet wet strength is shown in theTable 8 below.

TABLE 8 Pulp freeness Wet Tensile, lbs/inch Untreated Pulp Control 610csf  4.8 Treated with 2% 625 csf 10.9 peroxide, 0.04% ferrous sulfate

Example 9

A wet, Southern Pine Kraft pulp was treated with 1% hydrogen peroxide atpH 4 with 0.02% ferrous sulfate applied on pulp. The treatment was donein the mill scale in the bleach plant at 80° C. for 1 hour. In anothertreatment done in the lab, 3% peroxide was used with 0.04% ferroussulfate at 80° C. for 2 hours. The treated pulps and the control(production) pulp, without refining, were tested for carbonyl andcarboxyl groups. The results were shown in the following Table 9.

TABLE 9 Copper Number Carboxyl (meq/100 g) Control pulp 0.13 4.9 1%Peroxide 4.0 5.5 mill treated pulp 3% Peroxide 6.9 7.6 lab treated pulpAs shown in Table 9, 1% peroxide treated pulp has an increase in coppernumber (30 times higher) and in carboxyl groups (12% higher). A 3%activated peroxide intense treatment resulted in a 52 times highercopper number and 55% increase in carboxyl.

Example 10

Mill-dried Market Southern Pine Kraft pulp was re-pulped into pulpslurry. This pulp was treated with 2% hydrogen peroxide at pH 4 with0.04% ferrous sulfate at a temperature of 80° C. for 1 hour. The coppernumbers of the treated and untreated pulp were determined. The resultsare set forth in the following Table 10.

TABLE 10 Copper Number Carboxyl (meq/100 g) Control Dried Pulp 0.23 3.1Treated Dried Pulp 5.6 4.1The results set forth in Table 10 indicate, the treated pulp has 23times higher Copper number, and an increase of carboxyl by 32% ascompared to the untreated pulp control.

Example 11

The pulp slurry as in Example 11 was treated with 1% hydrogen peroxidewith 0.02% ferrous sulfate, at pH 4, 80° C. for 1 hour. The coppernumber was increased from 0.23 to 5.3. Both the treated pulp and thecontrol pulps were further treated high charge density polyvinylamineand were formed into Tappi hand sheets were made using the procedure ofTappi T 205 sp-02. The basis weight and caliper of the handsheets weredetermined by the procedures of Tappi T 410 om-02 and Tappi T 411 om-05,respectively and the bulk of control and treated pulps were calculatedfrom the basis weight and calipher. The results are set forth in thefollowing Table 11.

TABLE 11 Control Treated Control Pulp + 0.2% Treated Pulp + 0.24% Pulppolyvinylainine Pulp polyvinylamine Bulk, 1.79 1.84 1.83 1.91 cc/g

Example 12

A wet, bleached Southern Pine Kraft pulp was treated with 1% hydrogenperoxide and 0.02% ferrous sulfate at pH4 for 1 hour at 80° C. Both thetreated pulp and the control pulp were made into Williams hand sheets.The dried hand sheets were then fluffed by a lab-scale Kamas mill. Theliquid absorption capacity was tested (SCAN method). The results are setforth in the following Table 12.

TABLE 12 Control Pulp Treated Pulp SCAN Liquid 8.9 9.6 AbsorptionCapacity, g/g

From the results shown in Table 12, it is clear that the treated pulphas better liquid absorption capacity than the control pulp. In fact,this enhanced liquid absorption capacity, combined with the enhancedsouthern pine fiber collapsibility due to our activated peroxidetreatment, makes this treated southern pine pulp quite valuable in somehygiene products where super absorbent particles (SAP) are not used.

Example 13

“Mercerized Kraft Pulp” was formed by treating Southern Pine kraft pulpwith a caustic solution (10% concentration) for 5 minutes at atemperature of 40° C. The “mercerized pulp” was with 1% hydrogenperoxide in the presence of 0.02% ferrous sulfate at pH 4 and 80° C. for1 hour. The freeness treated and untreated mercerized pulp was evaluatedby the procedure of Tappi T 227 om-99 and average fiber length oftreated and untreated mercerized pulp was determined by a Kajanni. Thetreated and untreated mercerized pulp was formed into Tappi Hand sheetsusing the procedure of Tappi T 205 sp-02 and the basis weight andinternal bond of the hand sheets were determined by the procedures ofTappi T 410 om-02 and Tappi T 569 om-00, respectively. The bulk wascalculated from the caliper and basis weight as described above. Theresults bare set forth in the following Table 13.

TABLE 13 Average. Fiber Basis Internal Length, Freeness, Weight, Bulk,Bond, ft- L(L), CSF g/m2 cc/g lb/1000 sq ft mm Mercerized 730 160.3 2.7520 2.04 Southern Pine Kraft Mercerized 740 154.8 3.55 19 1.9 post-treated with 1% activated peroxide Untreated 740 2.53 Southern PineKraft

Example 14

An oxygen delignified Southern Pine Kraft pulp was treated with acellulose enzyme (Multifect A40 from Genencor) at a dose of 0.2% onpulp. This enzyme treated pulp was further treated with 1.5% hydrogenperoxide with 0.02% ferrous sulfate at pH 4 and temperature of 80° C.for 1 hour. The freeness and average fiber length of treated anduntreated mercerized pulp were determined by the procedures used abovein the examples. The treated and untreated pulps were formed into afibrous web and the web fluff shredded using Kamas lab scale hammermill.The fluff shredding energy determined. The results are shown in Table14.

TABLE 14 Average FQA Fluff Freeness, Fiber Length, Shredding CSF L(L),mm Energy, KJ/kg Untreated 743 2.68 223 Southern Pine Enzyme Treated 7402.6 — 2.13 Enzyme-treated, 740 2.61 201 then post-treated 607 1.26 with1.5% 470 1.07 activated peroxide

Example 15

Linerboard grade southern pine Kraft (kappa 110) that 2% activatedperoxide treatment of a low-cost with 0.04% ferrous sulfate at pH4 and 1hour at a temperature of 80° C. The freeness of the treated pulp wasdetermined using the procedure described in the above examples. Forcomparison purposes the freeness of a mixture of 80% untreatedhardwood/20% untreated southern pine was also evaluated. Tappi handsheets formed from 100% treated southern pine and formed from a mixtureof 80% untreated hardwood/20% untreated southern pine were evaluated todetermine Gurley Porosity (Tappi T 536 om-02) and the average PHST(Tappi T 530 om-02 with a phenolic resin liquid), respectively. Theresults are set forth in the following table 15.

TABLE 15 80% Hardwood/ 100% Treated 20% Pine Pine Freeness, CSF 600 682(fiber length 2.3 mm) Density 11.9 12.5 Gurley Porosity 22.1 22.9 Ave.PHST, seconds 60 per side 29 per sideThe data in table 15 shows that treated southern pine pulp can be usedto replace all the low-yield hardwood in saturating kraft paper.

Example 16

A bleached Southern Pine Kraft pulp was mixed with 2% hydrogen peroxidewith 0.02% ferrous sulfate at pH 4, pH 7, and pH 12 respectively. Thepulps at 1% consistency were under constant stirring at roomtemperature. A quartz plate was placed on top of the pulp slurry. Abench-top PS2 Ultraviolet device (medium pressure mercury lamp) was usedto irradiate the pulp slurry through the quartz plate. Fifteen minutesof UV irradiation were used in these treatments. After UV irradiation,no peroxide residuals were detected. The pulp temperature was notincreased by the treatment. The pulp viscosity was 3.2 cp for pH 4, 3.9cp for pH 7, and 10.6 cp for pH 10. The pulp treated at pH 7 has acopper number of 6.2.

Example 18

A bleached southern pine Kraft pulp was treated with iron, copper, orcombined Fe/Cu catalysts with hydrogen peroxide, at pH 4 and 80° C. for1.5 hours. The treated pulp and the control pulp were washed to pH 6 andmade into dry sheets. The dry sheets were then fluffed by the Hammermillas described previously and were tested for ammonia adsorption. Theresults of ammonia absorption were shown in the following table 17below.

TABLE 17 Pulp Ammonia gas % Viscosity, concentration Ammonia cp. inheadspace reduction Untreated Control Pulp 21.4 300 ppm NH3 — Treatedwith 1% peroxide,  4.5  50 ppm NH3 83%  0.03% ferrous sulfate Treatedwith 2% peroxide,  3.9  26 ppm NH3 91%  0.03% ferrous sulfate Treatedwith 3% peroxide,  3.2  11 ppm NH3 96%  0.04% ferrous sulfate Treatedwith 1% peroxide,  9.7 130 ppm NH3 57%  0.04% copper sulfate Treatedwith 1% peroxide,  7.2 105 ppm NH3 64%) 0.04% copper sulfate Treatedwith 2% peroxide,  5.7  41 ppm NH3 86%  0.04% copper sulfate Treatedwith 2% peroxide,  5.5  48 ppm NH3 84%  0.04% copper sulfate Treatedwith 2% peroxide,  8.9  80 ppm NH3 73%  0.02% copper sulfate Treatedwith 2% peroxide,  6.5  75 ppm NH3 74%  0.02% copper sulfate Treatedwith 2% peroxide,  3.2  15 ppm NH3 95%  0.03% ferrous sulfate, 0.02%copper sulfate

Finally, variations from the examples given herein are possible in viewof the above-disclosure. Therefore, although the invention has beendescribed with reference to certain preferred embodiments, it will beappreciated that other compositions may be devised, which arenevertheless within the scope and spirit of the invention as defined inthe claims appended hereto. The foregoing description of various andpreferred embodiments of the present invention has been provided forpurposes of illustration only, and it is understood that numerousmodifications, variations and alterations may be made thereto withoutdeparting from the spirit or scope of the invention as set forth in thefollowing claims.

1-29. (canceled)
 30. A personal hygiene article for absorbing fluids,the article comprising: at least one fluid permeable top sheet layer andat least one substantially fluid impermeable back sheet layer; and anabsorbent sub layer material interposed between the top sheet layer andthe back sheet layer, the sub layer material comprising a treatedbleached Kraft pulp; said treated bleached Kraft pulp made by a processcomprising treating a Kraft pulp with a catalyst in the presence of anoxidizing agent at an acidic pH.
 31. The personal hygiene article forabsorbing fluids according to claim 30, wherein the treated bleachedKraft pulp has a copper number equal to or greater than about
 3. 32. Thepersonal hygiene article for absorbing fluids according to claim 30,wherein the treated bleached Kraft pulp has a copper number equal to orgreater than about 4.4.
 33. The personal hygiene article for absorbingfluids according to claim 30, wherein the treated bleached Kraft pulphas a copper number equal to or greater than about
 5. 34. The personalhygiene article for absorbing fluids according to claim 30, wherein thetreated bleached Kraft pulp has a copper number equal to or greater thanabout 5.5.
 35. The personal hygiene article for absorbing fluidsaccording to claim 30, wherein the treated bleached Kraft pulp has acarboxy number equal to or more than about 3.5 meq/100 grams of ovendried treated pulp.
 36. The personal hygiene article for absorbingfluids according to claim 30, wherein the treated treated bleached Kraftpulp has a carboxy number equal to or more than about 4 meq/100 grams ofoven dried treated pulp.
 37. The personal hygiene article for absorbingfluids according to claim 30, wherein the treated treated bleached Kraftpulp has a carboxy number equal to or more than about 5 meq/100 grams ofoven dried treated pulp.
 38. The personal hygiene article for absorbingfluids according to claim 30, wherein the treated treated bleached Kraftpulp has a carboxy number equal to or more than about 5.5 meq/100 gramsof oven dried treated pulp.
 39. The personal hygiene article forabsorbing fluids according to claim 30, wherein the catalyst comprisesat least one of copper and iron.
 40. The personal hygiene article forabsorbing fluids according to claim 30, wherein the peroxide is hydrogenperoxide.
 41. The personal hygiene article for absorbing fluidsaccording to claim 30, wherein said treated bleached Kraft pulp is madeby a process comprising treating a Kraft pulp with a catalyst in thepresence of an oxidizing agent at pH of from 2 to
 6. 42. The personalhygiene article for absorbing fluids according to claim 30, wherein thecatalyst comprises iron.
 43. The personal hygiene article for absorbingfluids according to claim 30, wherein the treated bleached Kraft pulphas a viscosity of equal to or less than about 15 cps.
 44. The personalhygiene article for absorbing fluids according to claim 30, wherein thetreated bleached Kraft pulp has a viscosity of equal to or less thanabout 12 cps.
 45. The personal hygiene article for absorbing fluidsaccording to claim 30, wherein the treated bleached Kraft pulp has aviscosity of equal to or less than about 10 cps.
 46. The personalhygiene article for absorbing fluids according to claim 30, wherein thetreated bleached Kraft pulp has a viscosity of from about 1 to about 10cps.
 47. The personal hygiene article for absorbing fluids according toclaim 30, wherein the treated bleached Kraft pulp has a viscosity offrom about 2 to about 7 cps.